Trolley retarder for power and free conveyors

ABSTRACT

A trolley retarder for power and free conveyor systems comprising separate brake devices mounted on opposite sides of the conveyor track and adapted to engage and to frictionally retard movement of work carrying trolleys along the track.

United States Patent Aksamit [s41 TROLLEY RETARDER m POWER AND FREE CONVEYORS [72] inventor: Stephen M. Altsamlt, Melvindale,

Mich.

[131 Assigne e: Standard Alliance Industries, Inc.,

Chicago, Ill.

[22] Filed: Aug.26, 1970 [2]] App]. No.: 67,063

[52] U.S. Cl. ..104/250, 104/172 S, 188/62 [51] Int. Cl .L ..B61h 13/00, 8611: 7/00 [58] Field of Search.....104/l72 S, 178, 96, 249, 250,

[56] References Cited UNITED STATES PATENTS 3,056,360 10/1962 Burmeister etal. ..104/96 [151 3,705,554 [451: Dec. 12, 1972 823,772 6/1906 Fitch, Jr. 1 88/62 3,164,224 1/1965 Williamson etal ..188/62 3,503,471 3/1970 Balke ..188/57 FOREIGN PATENTS OR APPLICATIONS 938,071 l/l956 Germany ..l88/62 Primary Examiner-Gerald M. Forlenza Assistant Examiner-Robert Saifer Attorney-Harness, Dickey & Pierce [5 7] ABSTRACT A trolley retarder for power and free conveyor systems comprising separate brake devices mounted on opposite sides of the conveyor track and adapted to engage and to frictionally retard movement of work carrying trolleys along the track.

5 Claims, 3 Drawing Figures PATENTED 12 I972 3. 705, 554

' v w EE W INVENTOR.

TROLLEY RETARDER FOR POWER AND FREE CONVEYORS BACKGROUND OF THE INVENTION Although it has general utility, the retarder mechanism of this invention is primarily adapted and pre-eminently suited foruse on a power and free conveyor system of the type disclosed in the Czarnecki U.S. Pat. No. 3,415,201. In this type of system,work carriers having interconnected front and rear trolleys are adapted to move along a conveyor track which comprises laterally spaced opposed channels. Workpieces are suspended from the trolleys .or from a coupling bar which interconnects thetrolleysrln the power and free system shown in the patent referred to above, the disclosure of which is incorporated by reference herein, the front trolley of each work carrier is provided with spaced flop dogs whichtrap. a spring loaded, pivoted, depending drive lug on an overhead drive chain-so that the carrier is dragged along the track by the chain. The rear trolley of each work carrier has a cam plate which isshaped to nest with the front flop dog on a following carrier and in doing so itdisengages the following carrier from the associated drive lug and from the drive chain. It will be understood, however, that the work carriers aremoved along the track in spaced apart relation by the drive chain except .under special circumstances such as at a switch-over point from one conveyor to another or in a close-pack section of the conveyor where the carriersare disengaged automatically from the drive chain for somespecial purpose.

Difficulty has been encountered on occasion with-the carrier drifting or coasting or moving foronereasonor another particularly in those sections of the conveyor system where the carriers are disengaged from the drive chain. For example, as disclosedin-the copending application, Ser. No. 854,817, filed Sept. 3, 1969, at a switch-over point between two conveyors, work carriers are pushed up to the switch by the pivoted chain drive lug. At that point, the drive chain bends away from the conveyor tracks and when the drive lug drive lug push the carrier sufficiently far so that the front trolley moves entirely through the switch and onto the second conveyor track whereit sits'for a short period of time until a drive lug of the second conveyor comes along and picks it up. However, it sometimes happens that the second drive lug of the firstconveyor acting on the cam plate pushes the work carrier sufficiently so that it coasts through the switch and entirely onto the track of the second conveyor. This can happen under circumstances which cause a jam-up on the second conveyor. Also, as a second example, in situations where a long pendulous work carrying member is suspended from the trolley, the work carrying member may begin to swing when the trolley is released by the drive chain and the pendulum effect of the member may cause the carrier to move on through the switch before the second conveyor is ready to receive it. Then again, in close-pack areas of the conveyor, a following system. Further, in order to adapt the retarder for the varying needs and conditions existant in the system, it is necessary that it be easily adjustable between one extreme condition in which it prevents the carriers from :moving on the conveyor track unless they are positively connected to the power drive and theother extreme conditionin which it lets the carriers move slowly under their own weight and momentum as well as various intermediate conditions depending on the particular facts and circumstances. As a practical matter, it is necessary also that the retarder be essentially simple in design and operation so that it can be easily installed at various and sometimes difiiculty accessible locations in the system, it must engage and control the work carriers without causing excessive wear either on the carri er. or on the drag member of the retarder, and it must perform its intended function without adversely affect- .ing movement of the trolleys or the operation of any 1 part of the conveyor.

For example, retarders have heretofore been mounted at the top of the conveyor track so as to engage andfrictionally resist movement of work carriers along thetrack. However, these types of retarders have required that the trolley channels be cut into and in some instances thatthe top flange of the track channel be partially or occasionally entirely cut away. This in turn has produced serious jam-ups of equipment under certain conditions. Moreover, the track channelsare weakenedwhen portions of the channels are cutaway and particularly when the channel top flange is removed. The carrier trolleys sometimes tend to come up out of the track at the cut-aways particularly in close-pack sections where the carriers bump into each other. Each time something like this occurs, equipment is damaged and sometimes destroyed and extensive down time .of the entire system may result while the jam-up is beinglocated and corrected. This problem is obviated by the construction and mounting of the instant retarder.

SUMMARY OF THE INVENTION The retarder of this invention has separate stationary and movable brake devices which are adapted for mounting at opposite sides of respective channel track members with braking or drag portions of the devices disposed entirely below the channel lower flanges on which the work carriers travel. This arrangement positions the drag portions of the brake devices for engagement with the horizontal guide rollers of the carriers which is an ideal point of contactfor minimizing wear. The hardened peripheral surfaces of the guide rollers resist and minimize wear on the trolleys and the drag members that engage the trolleys preferably are equipped with wear resistant facings which minimize wear on the brake devices as well. In this connection, it will be appreciated, however, that the work carriers are braked or retarded only at selected points in the conveyor system and that the carriers usually are braked infrequently at widely scattered points in their travel around the system whereas each retarder acts on and checks the forward movement of every carrier that comes past it. Thus, the major wear occurs on the drag members of the brake devices and the latter therefore preferably are removable so that they can be replaced or repaired from time to time.

In the preferred mounting arrangement, the stationary and movable brake devices are mounted directly on their respective track channels with the drag members extending under the channel lower flanges and the facings of the drag members disposed between the inner edges of the channel lower flanges and in the path of travel of the work carriers. One or perhaps both of the two facings are beveled to gather the work carriers generally midway between the brake devices and to center the carriers between the channel track members and the brake devices as the carriers move through or past the retarder.

' The construction of the retarder provides a simple design for fabrication and the particular relationship between the retarder brake devices and the channel track members permits easy installation of the retarder even at difficulty accessible places in the conveyor system. No cutting into or weakening of the channel track members is necessary to accomplish the installation. Also, the particular construction of the retarder positions the removable and replaceable drag members below the channel lower flanges where they are readily accessible for servicing. More particularly, the com pact design of the retarder permits it to be mounted on or near a switch, on short load bar installations, and in a position which permits complete control of the carriers to be maintained at the switch point.

The movable brake device preferably is spring loaded in the direction of the opposite stationary brake device so that the two devices squeeze the work carriers as they move therebetween and provision preferably is made for adjusting the pressure on the spring so that the force exerted by the retarder on the work carriers can be selectively adjusted according to the exigencies and requirements of the particular situation. For example, it is desirable in certain situations for the retarder to bring the work carrier to a complete stop and to hold it until it is re-engaged with the drive chain or otherwise dragged positively through the retarder. In other situations, it is desirable that the retarder engage the work carrier only with sufficient force to slow down forward movement thereof while permitting it to coast slowly on through the retarder under its own weight and momentum. The retarder design and construction of this invention permits these extreme adjustments and any desired intermediate adjustment to be obtained easily and quickly.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary, perspective view showing a typical installation of a trolley retarder embodying the present invention on the channel tracks of a power and free conveyor system of the type hereinabove described;

FIG. 2 is a vertical sectional view taken on the line 2-2 of FIG. 1; and

FIG. 3 is a top plan view looking in the direction of the arrows 3-3 in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Attention is directed first to FIG. 1 which shows a fragmentary portion of a conventional power and free conveyor 8 having laterally spaced opposed channel members 10 and 12 which collectively define a conveyor track or way 13 for conventional work carriers two of which are shown at 14 and 46. Referring now again to FIG. 1, it will be observed that the channel 10 is arranged with the upper and lower flanges 16 and 18 thereof extending inwardly toward the channel 12 and that the latter is mounted with the upper and lower flanges 20 and 22 thereof extending inwardly toward the channel 10. Generally U-shaped hangers 24 and 26 straddle the channels 10 and 12; and the ends of the hangers are welded or otherwise fastened to the backs of the two channels. As shown, the hangers 24 and 26 extend substantially above the channels 10 and 12 and the upper portions thereof are attached to suitable supporting structure (not shown) from which the conveyor is suspended. In power and free conveyors of the type here under consideration, the channel track assembly usually is mounted on and supported or carried by roof or ceiling structural members. While only two hangers 24 and 26 are here shown, it will be readily appreciated that similar hangers are provided at spaced intervals along the entire length of the track 13 to hold the channels 10 and 12 uniformly and securely positioned.

Any of a number of different kinds of work carriers can be used in the conveyor system with the trolley retarder of this invention. Inasmuch as the particular work carrier here shown by way of illustration is the one disclosed in the Czarnecki U.S. Pat. No. 3,415,201, a detailed description thereof is not necessary as the disclosure of the patent is incorporated by reference herein. Suffice it to say that each carrier comprises a front trolley 28 and a rear trolley 30 which are interconnected below the channels 10 and 12 by a pivoted bar 32. The front trolley 28 has four vertical wheels 34, two at each side and two at the front and two at the rear which travel on the channel lower flanges l8 and 22. Front and rear pivoted flop dogs 36 and 38 on the trolley 28 normally trap the drive lug of an overhead power driven chain (not shown) which pulls or drags the carrier along the track 13. Front and rear horizontal wheels 40 (FIG. 2) also carried by the front trolley 28 travel between the channel lower flanges l8 and 22, as shown in FIG. 2, to hold the trolley normally centered between the channels 10 and 12 and to guide the trolley as it moves along the track and particularly around bends or curved sections thereof. The rear trolley 30 is similar to the front trolley 28 except that instead of the flop dogs 36 and 38, it carries a cam plate 42 which is utilized in transferring the work carrier 14 from one conveyor to another as disclosed in the copending application Ser. No. 854,817 hereinabove referred to and in disengaging following work carriers from the drive chain as disclosed in the Czarnecki patent also referred to above. For the latter purpose the cam plate 42 is provided with a rearwardly facing central recess or slot 44 which receives and nests with the front flop dog on the front trolley of a following carrier 46, as shown in FIG. 1. As the flop dogs of the following carrier move into the slot 44 and to the position shown in the drawing, a tapered surface or ramp 48 at the rear of the cam plate 42 raises the drive lug which normally is pivotally attached to the powered drive chain.

It will be understood that work carriers 14, such as the ones shown at 14 and46 in FIG. I, normally are connected to the drive chain in spaced apart-relationship and that they maintain this spacing during most of their travel in the conveyor system. It is only in certain relatively small sections of the system that the carriers are disengaged from the drive chain or close-packed as shown in the drawing. There are many reasons why it may be desirable to close-pack work carriers in a selected portion of a conveyor system as when the carriers are moved through a drying oven following a paint spray booth, for example, or where it is desired to store a number of work carriers for some reason.

In practice, the front work carrier in a close-pack section may be disengaged from the drive chain in any suitable or conventional manner as by a stop mounted on or alongside the track which disconnects the drive lug and lifts it out of engagement with the carrier or the chain drive and the trolley track 13 can simply be spaced sufficiently farther apart to disengage the drive lugs from the trolleys at the point in the system where the trolleys are to be close-packed. In FIG. 1 a positive stop 50 of a conventional type is shown for stopping the front work carrier in the close-pack section at a definite predetermined point. A stop of the type shown may be provided at a switch or transfer point between two different conveyors, for example.

The particular stop 50 here shown comprises a generally L-shaped rocker arm 52 mounted between two relatively closely spaced hangers 24 and 26. One arm 54 of the rocker arm 52 extends horizontally between the upper portions of the hangers 24 and 26 and is mounted on a pivot 56 carried by and extending between the hangers. Spacers 58 and 60 on the pivot 56 at opposite sides of the arm 54 hold the latter normally substantially midway between the two hangers 24 and 26. The other arm portion 62 of the rocker arm 52 extends downwardly between the hangers 24 and 26 to a position just above the channels and 12 and a stop block 64 on and extending inwardly from the lower end of the arm portion 62 has a tapered stop 66 thereon which is movable to a position between the flop dogs 36 and 38 to prevent movement of the carrier along the track. As shown, the horizontal arm portion 54 extends beyond the pivot 56 and a suitable actuator 68 such as a solenoid or air cylinder is operatively connected thereto. In the arrangement here shown, the lower end of the actuator 68 is supported on and attached to a mounting plate 70 which extends between and is carried by the hangers 24 and 26; and the extensible and retractable upper end of the actuator is pivotally attached to the end of the arm 54 by a clevis 72.

In operation, the actuator 68 preferably acts positively in both directions both to extend and to retract the clevis connector 72. When the clevis connector 72 is retracted, the arm 52 rocks about the pivot 56 in a clockwise direction, as shown in FIG. 1, to pull the stop 66 out from between the flop dogs 36 and 38 of the front carrier 14 thus permitting the latter to roll out of the close-pack section. Any suitable means can be provided for inducing forward movement of the front carrier such as the track channels 10 and 12 being inclined. On the other hand, when the clevis connector 72 is positively extended, it rocks the arm 52 in a counterclockwise direction as shown in the drawing to position the stop 66 over the space between the track channels 10 and 12 where it will engage and stop the first work carrier that moves to the position of the carrier shown at 14. In this latter connection, it will be readily apparent that as the front trolley of the carrier approaches the stop 66, the front flop dog 36 thereof will duck under the stop 66; but, when the rear dog 38 contacts the stop, the carrier is prevented from further movement and is held securely in this position until the stop 66 is removed in the manner hereinabove described.

Any suitable and conventional controls can be provided for operating the actuator 68 as for example a limit switch (not shown) mounted alongside the track for engagement by a work carrier approaching the positive stop 50. In this connection, it will be readily appreciated that a limit switch of the type described can be connected fordirect control of a solenoid type of actuator 68 or it can be operatively connected to an air cylinder type of actuator through the usual solenoid valve mechanism.

The trolley retarder 74 of this invention is here shown mounted on the channel tracks 10 and 12 in a position to control forward movement of the second work carrier 46 in a manner which prevents this carrier from following too closely after the lead carrier when the latter is released for movement into the conveyor system in the manner hereinabove described. It will be readily apparent, however, that the retarder 74 can be mounted at any desired location in the conveyor system and that it can be positioned on or adjacent to the channel tracks 10 and 12 and in any desired relation to adjacent control equipment. When mounted in the position shown in FIG. 1, the retarder is disposed substantially midway between the positions occupied by the front and rear trolleys of the following work carrier 46; and when the positive stop 50 releases the preceding carrier 14 the retarder engages the rear trolley of the carrier 46 with sufficient drag to give the preceding carrier ample time to coast out of and to clear the close-pack section. Thus, the preceding carrier is well out of the way by the time the following carrier 46 has progressed sufficiently far to trip the limit switch control and reset the positive stop 50.

As suggested, the trolley retarder 74 comprises a stationary brake device 76 and a movable or adjustable brake device 78 mounted on opposite track channels 10 and 12, as perhaps best shown in FIG. 2. The channels l0 and 12 are shown in phantom line in FIGS. 2 and 3 to permit full illustration of the brake devices 76 and 78; and in FIG. 2 the trolley and one of the horizontal rollers 40 thereof is shown in phantom lines for the same reason.

In any event, the stationary brake device of this invention comprises a mounting plate 80 on the back or outer side of the channel 12 and welded or otherwise attached solidly thereto. Studs 82 carried by the mounting plate 80 extend horizontally outwardly therefrom and through openings in the vertical flange 84 of an angle member 86. The other flange 88 of the angle member 86 extends inwardly below the lower flange 18 of the channel 12; and a facing strip 90 of a steel-brass alloy or other tough wear resistant material l060l0 o sa on the free edge of the flange 88 projects inwardly beyond the free edge of the channel lower flange 18. Spacers 92 interposed between the mounting plate 80 and the vertical angle flange 84 permit relatively accurate positioning of the facing 90 in the space between the channels and 12. Nuts 94 on the projecting ends of the studs 82 hold the angle member 86 normally attached securely to the mounting plate 80 but permits ready removal thereof for servicing or replacement in the event it is damaged by a jam-up or other accident or in the event of excessive wear on the facing 90.

The adjustable brake device 74 comprises a mounting plate 96 on the outer or back side of the channel 10 opposite the stationary brake device 76. As shown in FIG. 2, the mounting plate 96 preferably is welded or permanently and fixedly attached to the channel 10. Attached to the mounting plate 96 at opposite sides thereof are laterally spaced upright supports 98 and 100 which carry a depending bar 102 attached thereto by a transverse pivot 104. The supports 98 and 100 extend above the mounting plate 96 and the pivot 104 is located in the upwardly extending portions of the supports. The bar 102 swings about the pivot 104. Thus, when the bar 102 hangs straight down from the pivot it lays against the mounting plate 96 so that the latter limits inward movement thereof. On the other hand, the bar 102 is free to swing outwardly on the pivot 104 and away from the mounting plate 96. Welded or otherwise attached to the bar 102 below the mounting plate 96 and the upright supports 98 and 100 is a horizontal attaching plate or flange 106. The terminal portions of the attaching plate 106 extend substantially beyond the supports 98 and 100 and the projecting portions thereof carry screws 108 and 110 by means of which a wear plate 112 is detachably fastened thereto. Nuts 114 on the projecting lower ends of the screws 108 and 110 hold the wear plate 1 l2 normally attached securely to the flange 106 but permit the wear plate to be easily removed for replacement or repair. In any event, it will be observed that the wear plate 112 extends inwardly under the lower flange 22 of the channel 10 and that a facing strip 116 similar to the strip 90 on the stationary device 76 is provided thereon. The facing strip 116 extends inwardly of the free edge of the channel lower flange 22.

A stud 118 carried by and extending horizontally outwardly from the mounting plate 96 adjacent the lower end of the bar 102 projects through a clearance hole 120 in the bar. Disposed on the projecting end of the stud 118 at the outer side of the bar 102 is a compression spring 122 which is confined between the bar and a washer 124 by nuts 126 and 128 on the extreme outer end of the stud. Manifestly, the inner nut 126 can be advanced or retracted on the stud 118 to selectively tension the spring 122; and the nut 128 can be tightened against the nut 126 to hold or lock the latter in the selected adjusted position.

In operation, the compression spring 122 acts on the bar 102 to hold the latter normally in the innermost position against the mounting plate 96 but permits the bar to swing outwardly on the pivot 104. When the bar 102 is in the innermost position against the mounting plate 96 it positions the two facing strips 90 and 116 sufiiciently close together to obstruct or at least retard passage of a work carrier or trolley therebetween. As

suggested the brake devices 76 and 78 preferably are positioned to engage the hardened peripheral surfaces of the horizontal guide rollers 40 of the trolley, as

shown in FIG. 2, and the spacing between the facing strips and 116 in the innermost position of the bar 102 is less than the diameter of the guide rollers 40.

In order to permit the trolleys to pass readily into the space between the brake devices 76 and 78, at least one and if necessary both of the facing strips may be beveled as at 130 at the leading end thereof. In the particular form of the invention here shown by way of illustration, the facing 90 of the fixed brake device 76 is formed with a rounded corner 132 and the facing strip 1 16 of the adjustable brake device 74 is provided with a relatively long, flatly tapered bevel 130. Thus, when a work carrier moves between the brake devices 76 and 78 in the direction of the arrow 134 in FIG. 3, the guide roller 40 is or may be deflected slightly laterally away from the fixed brake device 76 and when the roller engages the lead-in taper 130 of the adjustable brake device 78 it wedges against the beveled surface to force the bar 102 outwardly against the spring 122. This movement of the bar 102 compresses the spring 122 and causes the roller 40 to be squeezed between the facing strips 90 and 116 with sufficient force to exert the desired control over the trolley.

It will be observed that the facing strips are relatively elongate and they preferably are sufficiently long to contact both the front and rear guide rollers of the trolley simultaneously. In normal operation, the front trolley of each carrier is moved past the retarder while the trolley is still connected to the drive chain. However, when the front trolley of the carrier moves into the slot 44 of the preceding carrier 14, it is disengaged from the drive chain in the manner hereinabove described. However, as soon as the front trolley of the following carrier moves past the retarder, the spring 122 returns the bar 102 immediately to the innermost position. Thus, the retarder is without effect at this point. However, when the preceding trolley is released from the close-pack section, the retarder engages the rear trolley of the work carrier 46 and prevents the latter from following too closely into the lead position.

It will be readily appreciated that when the retarder 74 is used in the manner hereinabove described, it is intended to provide only a light drag on the carrier but does not stop the trolley or prevent it from moving on the track 13. However, by a simple adjustment of the nut 126 or the use of a heavier spring 122, the amount of drag on the trolley can be selectively increased so that the retarder will stop movement of the trolley.

From the foregoing, it will be apparent that both the stationary and the adjustable brake device can be easily installed on the conveyor track. Very little space is required by the brake devices or for installation thereof, and they can be easily mounted in difficulty accessible locations on the track 13. Also, the design of the brake devices 76 and 78 is relatively simple which permits easy fabrication, assembly and mounting thereof. Parts of the brake devices 76 and 78 which are susceptible to wear are easily removable for servicing or replacement without affecting other more permanent parts of the assembly. Further, the desired amount of drag provided by the retarder can be easily obtained by a simple adjustment of the nut 126. Once the desired drag is obtained the brake device functions uniformly on all carriers without further adjustment or attention.

lclaim:

1. A trolley retarder for power and free conveyor systems of the type having a track in the form of laterally spaced, opposed channels provided with inwardly extending lower flanges and power driven work carrying trolleys provided with wheels which travel on said channel lower flanges and other wheels which travel between said channel lower flanges and present peripheral surfaces to the edges of said lower flanges to center and guide said trolley, said retarder comprising separate brake devices at opposite sides of and below said track, at least one of said brake devices being adjustably mounted for movement relative to the other of said brake devices, both of said brake devices having trolley engaging portions disposed below and extending inwardly of said channel lower flanges for mutual engagement with the peripheral surfaces of said other wheels of said trolleys; and

spring means coacting with said adjustable brake device urging the latter constantly laterally in the direction of said other brake device for pressed frictional engagement with opposite sides of said other wheels as said trolleys pass between said devices,

whereby said brake devices pinch said other wheels of the trolleys below said track and provide a drag to movement of the trolleys which is directly proportional to the force exerted on said adjustable brake device by said spring.

2. The combination as set forth in claim 1 wherein one of said brake devices is stationary and the other of said brake devices is pivotally mounted for movement relative to said stationary brake device, and wherein both of said brake devices are provided with wear resistant facings which physically engage the peripheral surfaces of the other wheels of said trolleys to retard movement thereof along said track.

3. The combination as set forth in claim 2 wherein said stationary brake device comprises a mounting plate fixed to the outer side of the channel with which it is associated, an angle member detachably fastened to said mounting plate and disposed with one flange thereof extending under and spaced from the lower flange of said associated channel, a wear resistantfacing strip on the inwardly extending portion of said angle member adapted to engage and to frictionally retard movement of a trolley on said track, and spacers interposed between said mounting plate and said angle member positioning the trolley engaging edge of said wear strip selectively inwardly with a respect to the lower flange of said associated channel. 4. The combination as set forth in claim 2 wherein said pivoted brake device comprises a mounting plate fixed to the outer side of the channel track with which it is associated, laterally spaced upright supports on and fixed to said mountin plate, a vertical ar pivoted to the mounting plates at the upper ends thereof and depending from said pivot mounting,

means forming a horizontal flange detachably fastened to the lower end of said bar and extending laterally below the lower flange of the channel with which it is associated, and

a wear strip on said horizontal flange normally projecting inwardly of said channel lower flange to engage a trolley moving on said track, and

wherein said spring means acts directly upon said bar to hold the same in frictional engagement with a trolley moving past said retarder on said track.

5. The combination as set forth in claim 4 including a stud on said mounting plate extending outwardly therefrom through an opening in said bar, wherein said spring means is mounted on the projecting portion of said stud at the outer side of and seating on said bar, and further including adjustable means on said stud coacting with said spring to regulate and control the force exerted by said spring means on said bar and consequently the drag of said retarder on said trolleys.

* 1K III 

1. A trolley retarder for power and free conveyor systems of the type having a track in the form of laterally spaced, opposed channels provided with inwardly extending lower flanges and power driven work carrying trolleys provided with wheels which travel on said channel lower flanges and other wheels which travel between said channel lower flanges and present peripheral surfaces to the edges of said lower flanges to center and guide said trolley, said retarder comprising separate brake devices at opposite sides of and below said track, at least one of said brake devices being adjustably mounted for movement relative to the other of said brake devices, both of said brake devices having trolley engaging portions disposed below and extending inwardly of said channel lower flanges for mutual engagement with the peripheral surfaces of said other wheels of said trolleys; and spring means coacting with said adjustable brake device urging the latter constantly laterally in the direction of said other brake device for pressed frictional engagement with opposite sides of said other wheels as said trolleys pass between said devices, whereby said brake devices pinch said other wheels of the trolleys below said track and provide a drag to movement of the trolleys which is directly proportional to the force exerted on said adjustable brake device by said spring.
 2. The combination as set forth in claim 1 wherein one of said brake devices is stationary and the other of said brake devices is pivotally mounted for movement relative to said stationary brake device, and wherein both of said brake devices are provided with wear resistant facings which physically engage the peripheral surfaces of the other wheels of said trolleys to retard movement thereof along said track.
 3. The combination as set forth in claim 2 wherein said stationary brake device comprises a mounting plate fixed to the outer side of the channel with which it is associated, an angle member detachably fastened to said mounting plate and disposed with one flange thereof extending under and spaced from the lower flange of said associated channel, a wear resistant facing strip on the inwardly extending portion of said angle member adapted to engage and to frictionally retard movement of a trolley on said track, and spacers interposed between said mounting plate and said angle member positioning the trolley engaging edge of said wear strip selectively inwardly with respect to the lower flange of said associated channel.
 4. The combination as set forth in claim 2 wherein said pivoted brake device comprises a mounting plate fixed to the outer side of the channel track with which it is associated, laterally spaced upright supports on and fixed to said mounting plate, a vertical bar pivoted to the mounting plates at the upper ends thereof and depending from said pivot mounting, means forming a horizontal flange detachably fastened to the lower end of said bar and extending laterally below the lower flange of the channel with which it is associated, and a wear strip on said horizontal flange normally projecting inwardly of said channel lower flange to engage a trolley moving on said track, and wherein said spring means acts directly upon said bar to hold the same in frictional engagement with a trolley moving past said retarder on said track.
 5. The combination as set forth in claim 4 including a stud on said mounting plate extending outwardly therefrom through an opening in said bar, wherein said spring means is mounted on the projecting portion of said stud at the outer side of and seating on said bar, and further including adjustable means on said stud coacting with said spring to regulate and control the force exerted by said spring means on said bar and consequently the drag of said retarder on said trolleyS. 